1. Field of the Invention
The present invention relates to a process for producing aromatic polyesters. More particularly, the present invention relates to a process for producing liquid-crystalline aromatic polyesters useful as raw materials for fiber, film and injection-molded parts, as well as covering material for optical fibers, because the polyesters have high elasticity, mechanical strength and toughness.
2. Description of the Related Art
Since aromatic polyester forming liquid crystal has a low coefficient of linear expansion, high elasticity and high strength, attention is paid to its various uses including covering material for optical fibers.
Regarding processes for producing such aromatic polyesters, a process in which polyester such as polyethylene terephthalate and polybutylene terephthalate is acid-decomposed with an acyloxy aromatic carboxylic acid such as p-acetoxy benzoic acid to produce polyester fragments and then the resulting fragments are copolymerized, is generally well-known (See Japanese Patent Publication No.18016/1981.)
In the process mentioned above, however, a large amount of insoluble, infusible matter regarded as a self-condensate of acyloxy aromatic carboxylic acid is undesirably generated. Therefore, the aromatic polyester has problems such as poor uniformity and inferior mechanical properties.